DESCRIPTION: Compliance with the medication regimen is a critical issue in the management of organ transplant patients. Although the limited available literature suggests that a minimum of 10 percent of all graft losses are due to noncompliance, with estimates ranging as high as 80 percent, research in this area has been inhibited by problems with access to large numbers of patients and good measures of compliance. The proposed research will use sophisticated monitoring techniques to assess the extent of compliance with immunosuppressant regimen in a large population of organ transplant patients. It will also identify correlates of noncompliance, evaluate related clinical events, and translate these findings into the design of an intervention program to increase organ transplant patients' compliance with their medication regimen. Four hundred subjects will be recruited from patients aged 18 years and older who received a solid organ transplant from January 1990 onward, who are at least six months post-transplant at the time they are recruited, and who are receiving tacrolimus (Prograf) as their immunosuppressant drug. Participants will be given a questionnaire to assess potential risk factors associated with noncompliant behavior (e.g., perceptions of self-efficacy and life control, social support, sociodemographic characteristics) and issues related to managing their medication regimen. Additional risk-related information will be extracted from their pharmacy profiles and medical records. Medication compliance will be assessed for the following six months by means of Medication Event Monitoring Systems (MEMS) caps on the subjects' tacrolimus vials. The MEMS cap records the date and the time of day that the vial is opened, so it is possible to assess the timing of doses as well as the fact that a daily dose was or was not taken from the bottle. Data will be analyzed to quantify compliance and to identify and quantify variables associated with noncompliant behavior. Information on clinical vents will be collected from medical and pharmacy records for the twelve-month period after compliance monitoring was initiated. Intervention program design will be based on results from this study indicating the appropriate target population and significant modifiable risk factors.